The subcellular distribution of cGMP-stimulated and calmodulin- sensitive cyclic nucleotide phosphodiesterases (PDEs) in bovine brain was studied. Although the cGMP-stimulated PDE has been purified to apparent homogeneity from supernatants of bovine hepatic, cardiac and adrenal tissues, in bovine brain this PDE is concentrated in particulate fraction of grey matter from cerebral cortex. Washed particulate fractions exhibit little apparent calmodulin-sensitive PDE activity, but in the presence of detergent considerable "latent" calmodulin-sensitive PDE activity was expressed. The detergent-solubilized, particulate cGMP- stimulated PDE was purified via cyclic nucleotide affinity chromatography and exhibits in SDS-PAGE an Mr slightly greater than the soluble form to the enzyme.